In conventional mattress structures, cushioning material such as a cotton batt is supported on a spring wire foundation comprising a plurality of spaced springs usually coil or sinuous springs tied together and generally arranged in substantially parallel rows along the length and width of the mattress. A cotton scrim may be sewed to the cushioning material for ease of handling.
In order to prevent "dimpling" and give more uniform support, a spring-bridging unit is applied between the cushioning material and spring wire foundation. The spring-bridging unit may be an open network of wire and rope or leno-weave cotton thread or burlap reinforced with wire strands. More recently, extruded plastic net has been employed as the spring-bridging unit.
U.S. Pat. No. 3,315,283 teaches the use of extruded plastic square mesh net which is heated and stretched to orient the plastic strands which thereby become stronger and stretch resistant. The oriented plastic net may be attached with a suitable adhesive to the mattress cushioning material as the spring-bridging unit for the spring wire foundation.
U.S. Pat. No. 3,562,825 discloses a mattress spring-bridging unit of extruded plastic square mesh net in which the longitudinal strands are thicker than the transverse strands that run across the width of the mattress. The relatively thick strands have a diameter of 0.066 inch and are arranged on 11/2 inch centers while the thinner strands have a diameter of 0.016 inch and are arranged on 1/4 inch centers. The thicker strands are not as highly oriented as the thinner strands.
U.S. Pat. No. 3,070,814 discloses the use of adhesive for securing the spring-bridging unit of U.S. Pat. No. 3,315,283 to the spring wire foundation.
U.S. Pat. No. 3,576,040 is directed to a spring-bridging unit of extruded plastic square mesh net using an adhesive plastic which may be directly bonded to the metal of the spring wire foundation. The longitudinal strands are thicker than the transverse strands. The longitudinal strands are arranged on 3/4 inch centers while the transverse strands are on 1/4 inch centers. The strands in the net are not oriented.
U.S. Pat. No. 3,579,774 discloses an extruded plastic square mesh net in which both sets of strands are oriented and the net is stitched to the cushioning material to form a spring-bridging unit. The strand size and spacing are the same as in U.S. Pat. No. 3,562,825.